In human medicine, doctors aim to prescribe antibiotics to patients only when needed, and when expected benefits outweigh the risk of  harmful side effects. Overusing antibiotics — prescribing too high of a dose, or using them to treat every issue that might be bacteria-related — can quickly give patients new health issues, and result in drug-resistant bacteria that are much more dangerous. The same idea applies to pesticides: when use is routine and widespread, the intended target (whether insect, plant, or fungus) is likely to evolve a resistance, all while the pesticides also cause lasting harm to other wildlife in the area.

Although using pesticides only when there is a verified need seems like a sensible strategy, applying pesticides “just in case” is commonplace.  However, this is beginning to change — in recent years, Québec has adopted this approach for seeds treated with neonicotinoid insecticides (“neonics”), with impressive results.

In 2019, the Canadian province prohibited the use of neonic-treated seeds for corn and soybean crops unless growers obtain a “prescription” from an independent agronomist. Like a doctor decides whether an illness warrants a prescribed medication, an agronomist determines if relevant soil pests are present at levels that could cause economic harm. Shifting to this “justification of need” framework was one of several stricter pesticide regulations implemented by Québec to protect pollinators and public health. 
 

Using pesticides “just in case” harms wildlife without helping agriculture

Before this landmark policy change, almost all of Québec’s corn and half of its soybean crops were grown from neonic-treated seed. In the United States, this remains the case. Nearly 100% of corn, 60-80% of soybeans, and about half of wheat crops are grown from seed coated with neonicotinoid insecticides. The high usage rates result from the "prophylactic", or “just in case”, use of neonic seed in fear of potential damage from crop pests. For these three crops alone, this means insecticide seed coatings are used on tens of millions of acres of land every year — whether or not there is a pest present. 

Prophylactic pesticide use assumes that all of the effort and costs involved will actually provide a benefit, such as having more crops to harvest. However, Québec’s policy change was motivated, in part, by a growing amount of research showing that using neonic-treated seed just in case, does not offer any economic benefit. For example, neonic-treated seeds didn’t have any benefit on crop yields for over 95% of corn and soybean fields in Québec, because pest populations were actually already low. In the United States, on-farm research trials on soybeans conducted by Practical Farmers of Iowa likewise found no benefit.

These are not outliers, either. Researchers at Cornell University released a comprehensive report on neonicotinoids, which examined over 300 studies and concluded that neonic seed treatments in corn and soy do not provide consistent benefits on how much grain is produced.  Another study conducted by Penn State Extension researchers found that neonic seed treatments actually decreased soy yield because they reduced the populations of the predators that would have eaten the pest insects. 

While the economic benefits of prophylactic seed treatments are in question, the ecological costs of widespread neonic use are well documented. Neonics are highly toxic to bees, and they are specifically implicated in wild bee population declines. Because only a small fraction of the pesticide coating is absorbed by the crop plant, over 90% ends up in soil, water, and plants elsewhere in the environment. As a result, neonics pose a growing threat to aquatic ecosystems and waterways. Neonic-coated seeds can also harm birds when eaten. The EPA itself has determined that the three neonics most commonly used as seed treatments put over 200 threatened and endangered species at risk of extinction.

Regulating pesticide-treated seeds benefits both growers and wildlife

So what happened in Québec once neonic seed treatments were prohibited? Former agronomist with the Canadian Ministry of Agriculture Louis Robert has described the successful transition away from neonicotinoid treated seeds and Québec’s corn and soy growers are reaching out to other regions to share their positive experience. In spite of vigorous opposition from seed companies and the pesticide industry (which are often one and the same), they were able to adjust quickly to the new market conditions. Claims that grain crops would fail were not realized, and yield has not been affected by the change. Since 2019, neonicotinoid detections have dropped in surface water sampling. Québec growers report that they are spending less by buying untreated seeds, as have soybean growers in Iowa who also have chosen to forgo insecticide seed treatments. 

In the US, a loophole prevents the EPA from tracking and regulating the use of pesticide seed treatments on the federal level, as they do for other pesticide applications. Unless this changes (which unfortunately seems unlikely), it is up to states to develop solutions to deal with excessive pesticide use. New York state heard this call and in 2023 passed the Birds and the Bees Act, which directs state agencies to develop a “justification of need” program analogous to Québec’s. Presently, Vermont is on the cusp of enacting similar legislation. In both states, the program is scheduled to go into effect in 2029. 

Prophylactic use of pesticide-treated seed is harmful to pollinators and ecosystems and it contributes to resistance, which in turn poses challenges for food production. Doing away with “just in case” treatments is a sensible way to reduce overall pesticide use, protecting both wildlife and crop systems. And it might put some money back in the pockets of farmers, too.

More Information

• https://www.xerces.org/pesticides/understanding-neonicotinoids
• Four key gaps in pesticide regulation for protecting pollinators